Without limiting the scope of the present invention, its background will be described in relation to setting packer assemblies, as an example.
In the course of completing a subterranean well, one or more packer assemblies are commonly installed at various locations within the well to isolate the wellbore annulus from the production tubing. Typically, a packer assembly incorporates a slip arrangement for securing the packer against the casing or liner wall and an expandable elastomeric element for creating a reliable hydraulic seal to isolate the annulus. In this manner, the packer assemblies are capable of supporting the production tubing and other completion equipment in the well and providing a seal between the outside of the production tubing and the inside of the well casing to block movement of fluids in the annulus to, for example, isolate a production interval.
Such production packers as well as other types of downhole tools may be run downhole on production tubing to a desired depth in the wellbore. Certain production packers may be set hydraulically by creating a pressure differential across a setting piston. For example, this pressure differential may be generated by creating a pressure differential between the fluid within the production tubing and the fluid within the wellbore annulus. This pressure differential shifts the setting piston to actuate the production packer into sealing and gripping engagement with the wellbore casing or liner. To prevent premature actuation of the setting piston, an actuator assembly including a rupture disc may be positioned in the flow path between the pressure differential. When it is desired to set the production packer, sufficient pressure may be applied to burst the rupture disc, thereby allowing the actuator assembly to operate and providing a fluid path for the differential pressure to operate on the setting piston.
As operators increasingly pursue more complicated completions in deep water offshore wells, highly deviated wells and extended reach wells, the use of rupture discs to create a downhole pressure barrier has become more difficult due to the lack of pressure headroom between the downhole hydrostatic pressure and the burst or collapse pressure of the downhole tubulars. Accordingly, a need has arisen for a downhole actuator assembly operable to selectively prevent and allow the application of a pressure differential to a hydraulically set downhole tool. A need has also arisen for such a downhole actuator assembly that is operable for use in complicated completions in deep water offshore wells, highly deviated wells and extended reach wells.